La-Mg-Ni-based alloys with A(2)B(7)- and A(5)B(19)-type main phases have been prepared by step-wise annealing method at various temperatures and times. When annealing at 1173 K, the alloy is composed of (La, Mg)(2)Ni-7 and (La, Mg)(5)Ni-19 super-stacking phases. Increasing annealing time from 15 to 25 hours at 1173 K causes the formation of LaNi5 phase at the cost of (La, Mg)(2)Ni-7 phase, while the (La, Mg)(5)Ni-19 phase abundance changed very little. When the annealing temperature rises to 1223 K, (La, Mg)(5)Ni-19 phase abundance increases drastically, indicating that (La, Mg)(5)Ni-19 phase abundance is more affected by annealing temperature than annealing time. Electrochemical P-C isotherms show that the alloys with only super-stacking phases have single plateau. The appearance of LaNi5 phase leads to an additional plateau which becomes more obvious as LaNi5 phase abundance increases. Electrochemical measurements show that higher (La, Mg)(5)Ni-19 to (La, Mg)(2)Ni-7 phase ratio benefits high rate dischargeablity (HRD) and cycling stability but suppresses the discharge capacity of the alloy electrodes. Besides, with increasing LaNi5 phase from zero to 15.1 wt.% in expense of (La, Mg)(2)Ni-7 phase, the maximum discharge capacity and cycling stability is deteriorated while the HRD, exchange current density, limiting current density and hydrogen diffusion coefficient are promoted. (C) 2013 The Electrochemical Society. All rights reserved.